Automatic exposure control system



y 1962 A. G. STIMSON ETA]. 3,033,093

I AUTOMATIC EXPOSURE CONTROL SYSTEM Filed June 30, 1958 3 Sheets-Sheet 1Allen G. Stimson J 0 ha H. Eagle Richard B Ferry Richard EBorderINVENTORS BY waxy/3 ATTORNEYS May 8, 1962 A. G. STIMSON ETAL 3,033,093

AUTOMATIC EXPOSURE CONTROL SYSTEM Filed June 50, 1958 5 Sheets-Sheet 2f/ss f7 0 4 i910 Fly. 11

Allen a. Stimson John H. Eagle RichardP. Ferry Richard E BorderINVENTORS BY {Mm MM ATTORNEYS AUTOMATIC EXPOSURE CONTROL SYSTEM FiledJune 50, 1958 3 Sheets-Sheet 5 Richard l g'r RichardEBo I' F g; 1INVENTORS %MZM BY frMw MW AT FORM United States Patent 3,033,093AUTOMATIC EXPOSURE CONTROL SYSTEM Allen G. Stimson, John H. Eagle,Richard I. Ferry,

and Richard E. Border, Rochester, N.Y., assignors to Eastman KodakCompany, Rochester, N.Y., a corporation of New Jersey,

Filed June 30, 1958, Ser. No. 745,469 17 Claims. (Cl. 95-64) The presentinvention relates to diaphragms for photographic cameras and moreparticularly relates to improved constructions for diaphragms that areautomatically regulated in response to changes in light intensity.

It is a common practice in motion picture and still cameras toautomatically regulate the size of a diaphragm opening as a function ofthe brightness of a scene that is to be photographed. Such regulation isusually referred to as automatic exposure control and typically employsa photocell for receiving light from the scene, a permanentmagnetmoving-coil instrument energized by the cell, and a diaphragm mechanismcoupled to the moving coil of the instrument. The current output of thecell varies with the intensity of light on it and in turn varies theenergizationof the instrument to adjust the diaphragm mechanism as afunction of the light intensity.

One of the simplest diaphragm mechanisms comprises a plane-polarizeddisk that moves with the coil of the instrument and is aligned with asecond plane-polarized disk and a fixed aperture in the light path ofthe camera. The moving coil adjusts the angle between the polarizationplanes of the two disks and thereby adjusts the amount of light admittedinto the camera. This diaphragm mechanism, although simple andrelatively rugged, is limited in its utility because it always uses themaximum aperture area of the camera and therefore provides a minimumdepth of focus.

A second diaphragm mechanism, in which the aperture area is varied andwhich therefore provides a greater depth of focus as the admission oflight is more restricted, comprises a single diaphragm vane moving withthe instrument coil and having a generally teardropor V-shaped aperturethat cooperates with a fixed aperture in the light path of the camera.As the coil moves in response to increased intensity of the incidentlight, the vane superimposes a narrower portion of its aperture over thefixed aperture. However, for settings of the single vane correspondingto middle and high values of light intensity, the moving apertureconstitutes either a narrow slit that completely crosses the fixedaperture or a small opening on one side of the fixed aperture;therefore, a substantial portion of the composite aperture overliesperipheral areas of the lens elements in the camera.

It is well known in the art that the use of the peripheral areas of theusual camera lens tends to degrade both the optical definition oftheimage and the uniformity of the light distribution in the focalplane. In order to overcome this objection many moving vane systems havebeen proposed in which two or more vanes, each having a teardropor V-shaped aperture are moved in opposition to each other, either by asingle instrument that is geared or otherwise coupled to both vanes, orby a plurality of instruments, one for each of the vanes. It isimmediately obvious that the cost, complexity, size, weight andfrequently the delicacy of such systems are increased along with the useof more than one moving vane, regardless of whether one or a pluralityof instruments are used to drive the vanes.

It is therefore a principal object of the present invention toautomatically control the aperture area of a camera by means of a singleelectrical instrument driving a single diaphragm vane having an aperturethat cooperates with a fixed aperture to form a composite, variableaperture, the major proportion of whose area is centrally located withrespect to the fixed aperture for all diaphragm settings.

A more specific object of the invention is to partially mask the fixedaperture of a camera to complement the variable masking due to anapertured diaphragm vane that is moved across the fixed aperture inresponse to variations in light intensity.

Other objects of the invention are:

To provide a manually removable partial mask over the fixed aperture ofa camera;

To provide a series of apertures of fixed graduated area with means forselectively aligning any of said apertures with the light path of acamera, in combination with a movable diaphragm vane that isautomatically positioned in response to'changes in light intensity andmeans for disabling the automatic positioning of the movable vane inresponse to the alignment of a predetermined one of the fixed-areaapertures with the light path of the camera;

To provide a partial mask for the fixed aperture of acamera, wherein themask comprises a plurality of generally V-shaped members having theirapexes extending toward the centra area of the fixed aperture; and

To provide a partial mask for the fixed aperture of a camera, wherein amovable diaphragm vane with a generally V-shaped aperture is adapted tocooperate with the fixed aperture to form a composite, variableaperture, with a cooperative relation between the mask and the vane forremoving the mask from the fixed aperture at a predetermined position ofthe vane.

Other objects of the invention will appear from the followingdescription, reference being made to the accompanying drawings, wherein:

- FIG. 1 is an exploded perspective view of a motion picture camerashowing the physical arrangement of the parts of a first embodiment ofthe invention;

- FIGS. 2, 3 and 4 illustrate the relative positions of the fixed andmovable apertures and the mask of FIG. 1 at typical aperture values;

FIG. 5 is an exploded perspective view of a manual override mechanismfor disabling the automatic exposure control system of the camera;

FIG. 6 shows a second form of mask for the fixed aperture of a camera;

FIG. 7 shows a moving diaphragm vane and its aperture for cooperationwith the fixed aperture and mask of FIG. 6;

FIGS. 8-14, inclusive, illustrate the relative positions of the fixedand movable apertures and the mask of FIGS. 6 and 7 at typical aperturevalues;

FIG. 15 shows a third form of mask for the fixed aperture of the cameraand shows a movable diaphragm vane adapted to cooperate with the fixedaperture and mask; FIG. 16 shows the cooperative relation between themask and the vane of FIG. 15, whereby the mask is removed from the fixedaperture at maximum-light settings of the diaphragm; and

FIGS. 1721,. inclusive, illustrate the relative positions of the fixedaperture, the mask and the diaphragm vane of FIGS. 15 and 16 at typicalaperture values.

Referring to FIG. 1, the invention is illustrated in the environment ofa motion picture camera, although it is understood that it may be usedequally well in a still camera. Light enters the camera and is focussedon the film 14 through an optional front lens element 10 and a rear lenselement 12, the latter of which constitutes a fixed aperture. The amountof light transmitted through the fixed aperture 12 is controlled by theposition of a diaphragm vane 16, which is formed preferably of thinaluminum and has an elongated and curved teardrop-shaped aperture 18overlying aperture 12. A lever 20 is pivoted viewfinder 42 of thecamera.

aesaoes $3 on a shaft 22closely parallel to vane 16, and has on one enda mask 24, which has the general shape of an inverted V. Mask 24overlies a segment'of aperture 12 extending from the periphery of thataperture to approximately its center. Preferably, the area of the maskis somewhat less than half the area of aperture 12. The extreme endofthe mask may be indented, as shown at 26, for a reason to be explainedhereinafter.

Diaphragm vane 16 is mounted on a coil 30 of a galvanometer-typeelectric instrument and rotates with the coil to align various portionsof aperture 18 with the fixed aperture 12. Coil 3G and its instrumentare well known in the art and are shown, for example, in U.S. Patent1,927,346, granted September 19, 1933, to L. E. Lawrence. Coil 30receives energizing voltage through a pair of control springs, one whichis shown at 32, from a photosensitive element 34 which may be of theusual photovoltaic type. Element 34 is exposed to the viewed scenethrough a lenticular lens system 36. It is well known that the angularposition assumed by a pivoted moving coil of an electric measuringinstrument, such as coil 30 of HG. 1, connected to the output of aphotovoltaic element, such as element 34, is a function of the intensityof the lightincident on the photosensitive element. The disposition ofdiaphragm vane 16 relative to aperture 12 is such that the width of theportion of aperture 18 aligned with aperture 12 by the movement of coil30 is an inverse function of the intensity of the light incident onelement 34.

A pointer 38 is integral with coil 30 and is rotated thereby forcooperation with an aperture scale 40 in a For simplicity ofillustration, scale 40 is shown as a reversed image of its usualappearance from the front of the camera.

Referring again to mask 24, it will be seen that for the higher aperturevalues, corresponding to the smaller diaphragm openings, the maskcooperates with vane 16 to form a composite aperture which issubstantially central ized over the fixed aperture 12. Thecentralization of the composite aperture is shown particularly in FIGS.3 and 4, wherein vane 16 is illustrated in its approximate positions foraperture values of "/11 and f/l6, respectively. it will be apparent thatin the absence of mask 24, vane 16'would have to be'moved further to theleft for each of these aperture values and would have to cooperate withthe lefthand periphery of the fixed aperture 12, thereby limiting thelight path primarily to a peripheral portion of aperture 12, which isundesirable for the reasons previously set forth.

In FIG. 4, in particular, it can be seen that the relieved portion 260imask 24 cooperates with the extreme inner surface of aperture 18 to forma centralized, composite aperture for the smallest diaphragm openings.

FIG. 2 illustrates the relative positions of apertures 12 and 18 andmask 24- for one of the larger diaphragm openings. Although in-this casea considerable portion of the peripheral areas of aperture 12 is used inthe light path, this portion is not as great as it would be in theabsence of the mask.

When the intensity of the viewed light is at so low a value that itcorresponds to an aperture value below the limit of scale 4%,mask24 maybe manually rotated away fromaperture- 12 by means of a finger knob 28(FIG. 1). For this purpose lever 2% is frictionally rotatable aboutitssha'ft 22. Kit is deemed unnecessary to remove mask 24 from aperture12, lever 20 may be eliminated and the mask may 'be formed as a fixedmember; for example, it may constitute an extension from the peripheryof'aperture 12.

FIG. illustrates one form of structural organization by means of whichthe automatic operation of the diaphragm vane of FIG. 1 may beoverridden manually for setting the diaphragm opening at any of a seriesof selected values. A disk 44 that is pivoted at its center along with ashaft 46 has a series of circular apertures 48 of graduated areasarranged with their centers at equal radial distances from shaft 46.Disk 44 is mounted on the camera by shaft 46 at a position such that acircle passing through the centers of apertures 48 also passes through aline normal to the center of the fixed lens aperture 12 (FIG. 1). AknobStl (FIG. 5) integral with shaft 46 may be used to rotate the shaftand disk for aligning any of the apertures 43 with aperture 12. Knob 5may be provided with a pointer 52 to cooperate with an aperture scale 54which is conveniently located on an outside surface of the camera.

Each of the two largest apertures 48 on disk 44 has approximately thesame diameter as the fixed aperture 12 of the camera and one of these isprovided with a mask 546 shaped like the previously described mask 24,shown in PEG. 1. When the masked aperture 48 is aligned with aperture 12its mask 56 performs the function of mask 24, and the cooperativerelation between the mask, the fixed aperture 12 and the moving vane 16is the same as described above in relation to FIG. 1. When disk 44 is.rotated to any other position, i.e., when any aperture 48 other thanthe-masked one is aligned with aperture 12, a cam 58, which is integralwith and approximately centered on the disk, cooperates with a lowersurface 60 of diaphragm vane 16 and maintains the vane in a positionwherein the maximum-Width portion of its aperture 18 is aligned withaperture 12, thereby preventing any automatic positioning of the vane;In this case, the size of the aperture 48 aligned with aperture 12controls the amount of light admitted into the camera, and the aperturevalue can be read from scale 54 rather than from scale 40. The structureshown in FIG. 5 is claimed in the copending application Serial No.812,477, filed May 11, 1959, which is a division of the presentapplication.

FIG. 6 illustrates a second masking structure that has been found toprovide a better centralizationof the composite aperture than the maskshownin FIGS. 1 to 5. A member 62, which corresponds to lever 20 of FIG.'1, has integral therewith a pair of opposed masks 64, each of which-hasthe general shape of a V with a truncated apex. The apexes of the masksextend toward each other from opposed peripheral areas of the fixedaperture '12 in the camera and form a somewhat hourglass-shaped aperture66 centralized over aperture 12. FIG. 7 shows a moving diaphragm vane 68having. an aperture 70 in the general shape of a stepped teardrop,adapted for cooperation with masks '64 and aperture 12 to control theadmission of light into the camera. Vane 68 may be moved in the mannerpreviously described in relation to vane 16 of FIG. 1, and member 62 maybe rotated to remove masks 64 from aperture 12 as previously describedin relation to lever 20 of FIG. 1.

FIGS. 8-14, inclusive, show the shapes of. the composite aperturesformed when vane 68 is rotated to various positions over mask 64. Eachbroken-line circle 72 in FIGS. 8-14 represents the ideal circularaperture havingthe same area as the composite aperture in that drawing.The position of vane 68 in each of FIGS. 8-14 is determined by thecoincidence of the center of the circle 72 and the intersection of thecurved center line 74 (FIG. 7) of aperture 70 and aline 76 normal toline 74. Each line 76 is designated by an aperture value correspondingto an aperture value assigned to one of the drawings of FIGS. 844. Itwill be seen that each composite aperture remains well centralized withrespect to masks 66 and therefore with respect to the fixed aperture 12'(FIG; 6) of the camera.

' FIG. 15 illustrates a third form of masking structure wherein twomasks 365 and 82 are similar in shape and location, relative to thefixed aperture 12, to masks 64 shown in FIG. 6. Masks 8t) and 82 arejoined by an arcuate third mask 84 and all three of the masks areintegral with a lever 86 which is pivoted at 88.; A spring 5.90jnormally maintains lever 86-against a fixed stop 100 as shown in FIG.15. I

A diaphragm'vane 102 is rotated about a pivot 104, as previouslydescribed, and has three arms. A first arm 105 carries a counterweight106. A second arm 108 has an aperture in the general shape of a curvedV, which cooperates with the fixed aperture 12 and with masks 80, 82 and84 to form a composite aperture for controlling the admission of lightinto the camera. A third arm 112 of vane 102 carries an ear 114 whichcooperates with an arm 116 on the mask lever 86. When vane102 is rotatedto its maximum-aperture position, car 114 engages arm 116 and rotateslever 86 clockwise, as shown in FIG. 16, to remove all three of themasks from the light path of the camera. When vane 102 is in any of itspositions corresponding to smaller apertures, as shown in FIGS-15 and17-21, there is no contact between ear 114 and arm 116, and spring 90(FIG. 15) maintains the masks 80, 82 and 84 in their positions coveringthe edges of aperture 12. It will be seen that the addition of thearcuate third mask 84 improves the centralization of the compositeaperture for most diaphragm openings and that the removal of the masksat the maximum aperture value enables full use of the fixed aperture.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

We claim:

1. Variable diaphragm apparatus for defining the exposure aperture ofthe taking lens of a camera, said lens having a first zone producingrelatively good optical definition and a second zone producingrelatively poor optical definition, said apparatus comprising incombination: a movable diaphragm member having an elongated, taperedaperture; means for moving said member within a range throughout whichthe optical axis of said lens passes through said elongated aperture;and a mask adapted to occupy a fixed position during at least part ofthe movement of said diaphragm member, said mask in its fixed positioncovering a portion of said second lens zone in alignment with saidtapered aperture, thereby defining,

for said lens, exposure apertures having higher ratios of first-zone tosecond-zone lens area than exposure apertures of corresponding sizesdefined for said lens solely by said tapered aperture.

2. The apparatus defined in claim 1, wherein said mask covers less thanhalf of the area of said lens.

3. The apparatus defined in claim 1, wherein said mask includes agenerally V-shaped member having an apex extending generally toward theoptical axis of said lens.

4. The apparatus defined in claim 3, wherein the apex of said V-shapedmember is indented.

5. Variable diaphragm apparatus for the taking lens of a camera,comprising: a movable diaphragm vane having an elongated, taperedaperture; means for moving said vane within a range, in each position ofwhich the optical axis of said taking lens passes through said taperedaperture; and means cooperating with said vane to define exposureapertures more centralized with respect to said optical axis thanexposure apertures of corresponding sizes defined solely by the portionof said tapered aperture optically aligned with said lens, saidlast-named means comprising a mask having a normal position in alignmentwith said elongated aperture and covering a peripheral portion of saidlens, said mask being adapted to remain in its normal position whilesaid vane is moved through at least a part of said range.

1 6. The apparatus defined in claim 5, having manually operable controlmeans cooperating with said mask for selectively moving the latter awayfrom said normal position in order to uncover said peripheral portion ofsaid lens.

7. The apparatus defined in claim 5, with: a first control surface onsaid mask; and a second control surface on said vane adapted to engagesaid first control surface, when said vane moves to a predeterminedposition, for moving said mask away from said normal position in orderto uncover said peripheral portion of said lens.

8. Variable diaphragm apparatus for the taking lens of a camera,comprising in combination: a movable diaphragm member having anelongated, tapered aperture; means for moving said member within apredetermined range throughout which the optical axis of said takinglens passes through said tapered aperture; and means cooperating withsaid diaphragm member to define exposure apertures of said lens havingoverall optical properties superior to those of exposure apertures ofcorresponding sizes defined by the entire lens area optically alignedwith said tapered aperture, said last-named means comprising a pair ofmasking members normally disposed in fixed positions covering peripheralareas of said lens on opposite sides of said optical axis and insubstantial alignment with said tapered aperture, said masking membersbeing adapted to remain in said fixed positions when said diaphragmmember is moved through at least a part of said range.

9. The apparatus defined in claim 8, wherein each of said maskingmembers is substantially V-shaped and has a respective apex extendinggenerally toward the optical axis of said lens.

10. The apparatus defined in claim 9, wherein the apex of each of saidmasking members is truncated.

11. The apparatus defined in claim 9, with an arcuate third maskingmember interconnecting said two masking members and overlying aperipheral area of said lens.

12. In a camera having a taking lens, a photoelectric cell adapted to beexposed to light from the exterior of the camera, and an electricinstrument connected to said cell and energized thereby in proportion tothe intensity of said light, said instrument including a movable coilhaving an initial position and being moved away from said initialpositon as a function of the energization of said instrument,automatically variable diaphragm apparatus for defining an exposureaperture of said taking lens, comprising in combination: a diaphragmvane having an elongated, tapered aperture, said vane being coupled tosaid coil and movable thereby within a predetermined range throughoutwhich the optical axis of said lens passes through said aperture; andmeans for increasing the ratio of axial to peripheral lens area withinthe lens portion optically aligned with said exposure aperture, relativeto the entire lens portion optically aligned with said tapered aperture,said last-named means comprising a mask having a normal position alignedwith said tapered aperture and with a peripheral portion of said lens,said mask being adapted to remain fixed in said normal position whensaid vane is moved through at least part of said range.

13. The apparatus defined in claim 12, wherein said mask includes asubstantially V-shaped member having an apex extending generally towardthe axial area of said lens when said mask is in its normal position.

14. The apparatus defined in claim 13 wherein the apex of said V-shapedmember extends generally in the direction of decreasing width of saidtapered aperture when said mask is in its normal position.

15. In a camera having a lens and a photoelectric cell, anexposure-aperture control comprising a first exposureaperture controlmember adapted to be adjusted relative to said lens in response tochanges in the amount of light impinging on said cell, said firstexposure-aperture control member having an arcuate opening therein, anda second exposure-aperture control member fixedly disposed relative tosaid lens, said second exposure-aperture control member having anopening provided with at least one inwardly projecting masking memberaligned with trol member.

16. Variable diaphragm apparatus for the taking lens of a camera,comprising in combination: a movable diaphragm member having anelongated, tapered aperture;

means for moving said member within a predetermined range throughoutwhich the optical axis of said taking lens passes through said taperedaperture; and means cooperating with said diaphragm member to defineexposure apertures of said lens having optical properties superior tosuch optical properties of exposure apertures of corresponding sizesdefined by the entire lens area optically aligned with said taperedaperture, said lastnamed means comprising at least one masking membernormally disposed in a fixed position covering a peripheral area of saidlens in substantial alignment with said tapered aperture, said maskingmember being adapted to remain in said fixed position when saiddiaphragm member is moved through at least a part of said range.

17. Variable diaphragm apparatus for the taking lens of a camera,comprising: a movable diaphragm vane having an elongated, taperedaperture; means ior moving said vane Within a range, in each position ofwhich the optical axis of said taking lens passes through said taperedaperture; and means cooperating with, said vane to define exposureapertures more centralized with respect to said optical axis thanexposure apertures of corresponding sizes defined solely by the portionof said tapered aperture optically aligned with said lens, saidlast-named means comprising a fixed mask aligned with said elongatedaperture and covering a peripheral portion of said lens. 7

References Cited in the file of this patent UNITED STATES PATENTS

